The invention relates to an apparatus for smoothing out the surface weight distribution of one or multilayer mats containing lignocellulose and/or cellulose with a binding agent dispersed therein for the manufacture of shaped articles, in particular in the form of wood chipboard, wood fiberboard or the like. A vertically adjustable reverse brushing unit extends over the width of the web and is associated with a mat carrier which is fed or charged via at least one scattering head.
In the apparatus known to the Applicant from EP-PS 0 336 098 B1, a distribution unit for the variable deflection of the incident mat particles is disposed in the mat particle return scattering path in front of the reverse brushing unit as seen in the running direction of the mat. The distribution unit consists here of several pendulum-like flaps arranged alongside one another. The axes of the flaps preferably extend perpendicular to the mat carrier and are coupled in phase, or at least partly phase-displaced, to a common drive.
In contrast, the reverse brushing unit expediently consists of a reverse brushing scattering roller extending over the width of the mat with its axis extending parallel to the mat carrier and perpendicular to the running direction of the mat carrier. The reverse brushing scattering roller is preferably driven at a high speed of rotation, with an expedient rotary speed lying for example at 300 rpm. In operation of this known apparatus it was found that in the course of time undesired accumulation processes and baking on processes occurred at the reverse brushing scattering roller and at the pendulum flaps, in particular when manufacturing gypsum and/or cement-bound board-like products, and that these accumulation and baking-on processes disturb the problem free smoothing of the surface weight distribution of one or multilayer mats and also require cleaning work which is time-consuming and expensive.
The invention is thus based on the object of providing an apparatus of the initially named kind which permits an operationally reliable and more uniform surface weight distribution of one or multilayer mats. This object is satisfied in accordance with the invention by an apparatus in which a vertically adjustable reverse brushing roller extends at least over a part of the width of the web. The vertically adjustable reverse brushing roller has flexible bristles of hydrophobic material associated with a mat carrier which is fed via at least one scattering head. The reverse brushing roller cooperates with a cleaning brush with flexible bristles running in the opposite direction, or with a cleaning strip. The cleaning brush is an apparatus for receiving and returning the rearwardly brushed mat particles to the metering bunker of the respective scattering head provided in the region of the reverse brushing roller.
If the reverse brushing roller is set with flexible bristles of the same length then a very accurate surface weight distribution of a flat one or multilayer mat arises, with a problem free interplay with the measuring apparatus and the apparatus for receiving and returning the brushed back mat particles.
Since, in the apparatus of the invention, operation always takes place with an excess of particles, even greater irregularities in the scattered bulk material can be compensated for without problem. This also has the consequence that no high requirement need be placed on the metering accuracy, because the reverse brushing roller always brings about the required volumetric compensation.
In the event of the preferred oblique positioning of the reverse brushing roller or rearward brushing roller with respect to the running direction of the respective mat carrier, one obtains the advantages of an advantageous additional mixing of the particles, of an improvement in the uniformity of the particles and also of more rapid discharge transport of the particles from the reverse brushing rollers back to the metering bunker of the respective scattering head.
An advantageous variant of the invention resides in that the reverse brushing roll can be so vertically adjustably fixed relative to the mat carrier that a mat of trapezium shape in cross-section can be generated for pressing into roof shingles and similarly shaped bodies.
In this connection it is particularly advantageous to arrange a reverse brushing unit above a profiled mat carrier which is of mirror image-like double wedge shape in cross-section, with the reverse brushing unit consisting of two reverse brushing rollers which in plan view form a displaced V-shaped arrangement. In this way a mat which is of double trapezium shape in cross-section can be manufactured which can be subdivided after a subsequent pressing procedure into two correspondingly shaped bodies. It is moreover important to the invention that the flexible brushes of the reverse brushing roll can also be of different lengths in order to give a mat a desired surface structure if, for example, one wants to manufacture a decorative wall plate or panel from it.
Advantageous design features and further embodiments of the invention are set forth in the subordinate claims.